Known wireless communication devices such as a typical mobile telephone or a tablet personal computer (PC) each typically includes one of several types of commercial transceiver or radios, such as multi-band cellular, Wi-Fi®, Bluetooth®, and Global Positioning System (GPS). Each of these transceivers includes an integrated circuit (IC), or collection of ICs designed for a specific wireless communication standard (e.g., the Bluetooth® standard). Furthermore, the wireless standards are defined by a group such as the Institute of Electrical and Electronics Engineers (IEEE) (e.g., Wi-Fi®), or by a consortium (e.g., Bluetooth®). Such wireless standards typically have mandatory modes that must be supported by an IC to be considered “compliant” with that standard. Compliance with the standard is used to provide interoperability among devices from different manufactures. Because of the complexity of these standards, and the “overhead” circuits used to support at least the mandatory functionality of the standard, transceiver ICs that are standard-compliant typically consume higher power than custom transceivers that do not target any specific standard. For example, a Bluetooth®-compliant transceiver from Texas Instruments (TI) typically consumes >40 mW in the active mode, while a proprietary transceiver from Energy Micro consumes <10 mW.
Any wireless peripheral device such as, for example, a headset or a stereo, that wirelessly connects to a wireless communication device typically does so using one of the wireless connectivity standards the wireless communication device supports (e.g. iPhone®, Wi-Fi® and Bluetooth®; Galaxy SIII®; Wi-Fi®, Bluetooth®, and Near Field Communication). This means the wireless peripheral device typically also uses a standard-compliant IC to provide interoperability between the wireless communication device and the wireless peripheral device. While the wireless communication device can typically be recharged periodically (e.g., nightly), wireless peripheral devices are not recharged as frequently, they typically operate for longer periods of time off a single charge, and they usually are powered by smaller batteries than those in the wireless communication device. Therefore, it is desirable for the power consumption of the transceiver on the wireless peripheral device to be significantly smaller than that of the wireless communication device, and it is desirable for the power consumption on the wireless peripheral device to be adequately managed so as to provide long battery lifetime.
Wireless peripheral devices typically can either set their transceivers into a low-power “sleep” mode, or turn them off entirely, to reduce the power consumption. This is typically referred to as “duty cycling”. Problematic situations, however, can arise when a wireless communication device attempts to wirelessly communicate with the wireless peripheral device during such “sleep” and/or “off” modes when the wireless peripheral device's transceiver is powered off and unable to receive messages from the wireless communication device. This presents a tradeoff between the latency in communicating with a wireless peripheral device, and the power consumed by the wireless transceiver on the wireless peripheral device. More frequent turning on of the wireless transceiver leads to lower latency, but higher average power consumption, and vice versa.
Accordingly, a need exists for apparatus and methods that allow a wireless communication device to wirelessly communicate with a wireless peripheral device while the wireless peripheral device is in a low power “sleep” mode, with its main wireless transceiver in the “sleep” or “standby” mode.